The incident, along with a July 5 fatal police shooting in Baton Rouge, Louisiana, sparked protests and debate about police-community relations.

"That's his right, to plead not guilty," John Thompson, a friend of Castile, said Monday. "It is what it is, we want everything to be fair and just."

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During the traffic stop, Castile, 32, told the officer he was legally carrying a gun, but "the mere presence of a firearm alone cannot justify use of deadly force," Ramsey County Attorney John Choi said.

Yanez told investigators he thought Castile had the gun in his hand and there was "no option" but to shoot.